Eradication of amebiasis in a large institution for adults with mental retardation in Taiwan.

Investigation of a program to eradicate amebiasis using consecutive intensive mass screenings followed by medication in a large institute for adults with mental retardation in Taiwan. Prospective cohort study, with 3 years of follow-up. A large, 450-bed institution for adults with mental retardation located in southern Taiwan. All 443 adults with mental retardation in the institution, who have various motor and/or mental handicaps, were included in this study. A total of 7 consecutive intensive mass screenings for amebiasis for all residents (performed in March, August and November 2001, March and August 2002, January 2003, and May 2004). Infected patients were treated using the standard protocol of the Center for Disease Control of Taiwan. Enzyme immunoassay testing was used for the amebiasis screening, with the rapid detection of the specific antigen for Entamoeba histolytica in human fecal specimens confirmed by microscopic examination. The serial prevalence and cumulative incidence were then calculated. The prevalence of amebic infection declined in serial screenings, but new infections and reinfections were detected in 5 of 6 follow-up screenings. The prevalence was 10.8% at the beginning of the program and then gradually reduced, falling to 6.3%, 3.6%, 2.7%, 3.4%, and 2.2%. Finally, no more positive cases were identified in the last screening (May 2004). The cumulative incidence rate stabilized at around 40% by the fifth screening. Of the 179 infected patients, 120 had primary infections, with 59 cases of multiple amebic infections. Active surveillance with intensive mass screening is an effective method of identifying asymptomatic and latent cases of amebiasis in areas where it is endemic, such as an institution for adults with mental retardation.